Preferably multiple bus coupling devices are connected to the bus line, which are used to connect subscribers to the bus line. Each subscriber can be addressed via the bus line. The subscribers can include sensors and/or actuators. As a result of the bus communication device, it is possible for a host computer to communicate with the subscribers, for example to receive data from the subscribers or transmit data to the subscribers. Bus communication devices, such as a Foundation Fieldbus H1 system or a Profibus PA system, are known.
EP 1 819 028 A2 describes a redundant fieldbus system. Two fieldbus lines are provided in each case with a power supply unit there and are connected to a host. A bus coupling device is used to couple the subscribers to the bus lines. The bus coupling device is connected to the two bus lines, and thus also to the two power supply units. Subscribers can be redundantly connected to the bus coupling device so that each subscriber is connected to the two bus lines. In this way redundancy is achieved, so that communication via the respective other bus line is possible even when one bus line or one power supply unit fails. Simultaneous operation of the two bus lines is not possible because otherwise the wave impedance is cut in half by the parallel connections of two bus lines and no longer meets the requirements of the fieldbus protocol.